Problems Setting up Set Driven Keys (SDK)

[buho]

I've tried to use Set Driven Key multiple times in the past year, and they never work for me. Open Set Driven Key window, highlight destination object, click Set Driven, highlight source object, click Set Driver, select one attribute for each, click Set, close window. Driven object's attribute is orange now, meaning it's keyed. However, when I move the driver object, the driven object does not respond. Shouldn't the driven object move the instant I modify the diver object? I tried setting timeline keys on the driver to see if that works. Driver keys fine when I scratch timeline, but driven doesn't move! What am I doing wrong? I'm using Maya 4.0 Unlimited on WinXP.

I've gotten around this problem before by creating my own expressions that basically do the same thing:

    drivenObject.rx = driverObject.rx

however, I'm getting an error on this above code. It's been over half a year since I've written MEL. I'm thinking it might have something to do with scope, like it doesn't know where the driverObject I'm referencing is. (BTW, "drivenObject.rx = 3" works.) I could use a refresher in scope with MEL.

Thanks in advance for any help!

[mantrid]

thats not exactly what SDK is for.....if you want something to litterally drive something else, you eother constrain, or connect or expression attributes together. What a set driven key is for, is to remember animation based on a controller...a driver.

So, what you have done, is to save a key at default, and nothing else...hence, nothing happens, cos you havn't saved a set driven key in any other pose/positions.attribute values...so, no attribute value differences saved as a set driven key, then there is no animation for the sdk to "remember".

Example 1:

Make a ball and a cube and move the cube away in the x axis. Lod the cube into the SDK window as a driver and the ball in as driven. Select translate x as the driving attribute and translateY as the driven attribute.

Save a set-driven-key and keep the window open. Now, move the cube the same distance on the other side of the sphere and hit key. Now, move the cube to 000 where the ball is, and move the ball up higher than the cube in the trans Y. save another key, close sdk window. Now, when the cube passes under the ball, the ball jumps out the way. If you go to the animation>graph editor, you'll see a graph for the sdk. Altering this graph will allow you to customise the sdk, so, for example, the ball will not jump until the cube gets closer.

Example 2:

add an attirbute to a foot object. Call it footroll and give it min value of -5 and max of 10 and default 0. Load it into the sdk window as a driver and select the new attribute. ...now, assuming a VERY primitive foot setup for the purposes of the example, with just one bone for the foot....

.....load the foot bone in as the driven, and select rotate Z. Now, save a set-driven-key. Now, change the footroll attribute to -5 and then rotate the foot so the toe is up in the air a bit, as if the foot is on its heel. Save another key. Now, change the footroll attribute to 10 and rotate the foot till it is pointing down as far as you would percieve it to be able to. Save another key. Close the SDK window.

Now, if you select the footroll attribute and use your middle mouse button over the view window to slide the value back and forth, you'll see its effect.

SDK gives you an interesting level of limited control, that fills the gap between expressions and non-linear animation, without actually being either. It is a good way of setting up character automation such as complex footrolls, finger movements, moving parts of machines, etc etc.